1. Technical Field
The present invention relates to a device, a method for manufacturing such a device, and a method for forming a film.
2. Related Art
In recent years, liquid-phase processes for manufacturing electronic devices are being developed. The following documents disclose techniques for depositing materials, such as hole injection materials and luminescent materials, for forming organic electroluminescent (EL) devices on base members by droplet-ejecting processes: JP-A-2001-291583 (hereinafter referred to as Patent Document 1), JP-A-2002-56980 (hereinafter referred to as Patent Document 2), and JP-A-2004-235138 (hereinafter referred to as Patent Document 3).
FIGS. 15A and 15B schematically illustrates a known method for forming a film by a droplet-ejecting process. In the known method, as shown in FIG. 15A, a bank B is formed around a region for forming a film F. After the bank B is surface-treated to be lyophobic using CF4 plasma or the like, a liquid L containing a functional material is provided in the region surrounded by the bank B. The liquid L is then dried, whereby the film F containing the functional material is formed as shown in FIG. 15B.
Since the film F is formed using the bank B, there is a problem in that the film F has raised end portions F2 and F3 as shown in FIG. 15B and therefore is nonuniform. This is probably as described below. In general, edge portions of liquid droplets placed on base members are more quickly dried than inner portions thereof. Therefore, during the drying of each liquid droplet, the concentration of a solute in the edge portion of the liquid droplet first reaches saturation; hence the solute precipitates. In the inner portion of the liquid droplet, a solvent contained in the liquid droplet flows from a center portion of the liquid droplet to the edge portion such that the loss of the solvent is compensated. The solute in the center portion is transported to the edge portion by the solvent flow. The vaporization, of the solvent from the edge portion causes the salute to precipitate in the edge portion. If such a flow is created in the region surrounded by the bank B, surface portions of the film F that located near the bank B are raised and therefore the film F has an M or U shape in cross section. This leads to the deterioration of the flatness of the film F.
A layer formed on the film F having such a deformed shape has poor flatness and nonuniform thickness. In the manufacture of an organic EL device, a hole injection/transport layer and a light-emitting layer are formed in a region surrounded by each bank in that order. When the hole injection/transport layer is not flat, the light-emitting layer disposed on the hole injection/transport layer is not also flat. Therefore, the light-emitting layer has nonuniform light-emitting properties.
Patent Document 1 discloses a technique in which a flat layer is formed in such a manner that droplets are ejected by a droplet-ejecting process two times or more such that no recess or an uncoated portion is formed. Patent Document 2 discloses a technique in which a flat layer is formed using a leveling agent containing a silicon compound or a fluorine compound. Patent Document 3 discloses a technique in which a bank is formed on a hole injection/transport layer by patterning such that irregularities of the hole injection/transport layer have no influence.
The technique disclosed in Patent Document 1 has a problem that if the droplets ejected several times contain a single solvent, the selection of the solvent is limited because a primarily formed layer is dissolved in the solvent. The technique disclosed in Patent Document 2 has a problem that the leveling agent has influence on light-emitting properties. The technique disclosed in Patent Document 3 has a problem that if the bank is extremely high, drying occurs in various portions of droplets and therefore a formed layer has nonuniform thickness.